JP2646901B2 - Substrates for magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate for a magnetic recording medium such as a magnetic disk, and more particularly to a substrate for a magnetic recording medium suitable for a case where heating is required.

[0002]

2. Description of the Related Art Various types of magnetic recording media such as magnetic disks have been proposed and put into practical use. For example, Japanese Patent Application Laid-Open No. 61-13434 discloses a magnetic disk substrate using ceramic or cermet, and Japanese Patent Application Laid-Open No. 61-188733 discloses a method in which a nonmagnetic hardened layer and a magnetic medium layer are interposed. A magnetic recording medium provided with a non-magnetic underlayer is disclosed.

Further, Japanese Patent Application Laid-Open No. 62-20128 discloses a magnetic disk having a non-magnetic layer provided between a substrate and a magnetic layer, and discloses IEEE TRANSACTIONS ON MAGNE.
TICS, VOL. 24, NO. 6, November 1988 discloses a magnetic film in which an intermediate layer of chromium (Cr) is formed between two separate magnetic layers.

At present, hard disks and the like are manufactured by forming a magnetic alloy of chromium, cobalt (Co) or the like on a non-magnetic substrate. In order to promote the magnetic orientation of the magnetic alloy and increase the coercive force (Hc), a heat treatment by a heating process is performed before the chromium film is formed.

On the other hand, in recent years, the magnetic head tends to have a low flying height in order to increase the density of magnetic recording. For this reason,
Smooth glass substrates are being used because of the need to prevent collision between the magnetic head and the disk.

[0006]

However, when such a glass substrate is used, especially when it is transparent and the heating process for improving the magnetic characteristics described above is far-infrared heating, halogen lamp heating, etc. However, there is a disadvantage that light passes through the glass substrate and the heating efficiency is significantly reduced.

In order to increase the heating efficiency, for example, the transparent glass substrate may be made black. However, in this method, the additive must be mixed into the transparent glass substrate to make it black, which results in a significant increase in manufacturing cost as compared with the colorless transparent glass substrate.

The present invention pays attention to this point, and provides a magnetic recording medium excellent in mass productivity capable of efficiently heating and obtaining good magnetic characteristics even when a transparent glass substrate is used. It is an object of the present invention to provide a substrate for use.

[0009]

According to the present invention, there is provided a magnetic recording medium substrate having a magnetic film on which magnetic information is recorded formed on a transparent glass substrate. And a carbon layer having a thickness of 400 ° or more.

[0010]

According to the present invention, the carbon layer of the metal layer and 400Å or more thick, such as by 100Å or more thick chrome transparency glass substrate are respectively formed. By these, heating is performed well, and promotion of magnetic orientation of the magnetic film and high coercive force are efficiently performed.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a magnetic recording medium according to an embodiment of the present invention. a, Blackening of transparent glass substrate First, the blackening of the transparent glass substrate will be described. In this example, blackening was performed by the following three methods.

(A) Blackening with carbon alone First, as shown in FIG. 2 (A), blackening was attempted by forming only the carbon layer 12 on a transparent glass substrate 10 which was a non-magnetic substrate. The carbon layer 12 is 300-1100Å
The film was formed by a sputtering method with a film thickness of five steps between the steps. As a result, as shown in Table 1, although the density increased as the film thickness increased, all were black and transparent.

[0013]

[Table 1]

(B) Blackening by Chromium Base Metal Layer and Carbon Layer Next, as shown in FIG. 2B, first, a metal layer 14 of chromium is formed on a transparent glass substrate 10, and The carbon layer 12 was formed and blackening was attempted. Base metal layer 1
The chromium layer as No. 4 was formed by a sputtering method in four stages of film thickness between 100 and 450 °. Then, on each of the chromium layers of each thickness, 300 to 600
The carbon layer 12 was formed by a sputtering method with a four-stage film thickness between Å.

The thickness of the chromium layer was set to five levels between 500 and 1000 Å, and a 500 Å carbon layer was formed on the chromium layer of each thickness. In addition, 4 chrome layers
The thickness is fixed at 50 ° and the carbon layer is 500 to 1000
The film was formed in five steps between Å. Table 2 shows the degree of blackening of the sample obtained as described above.

[0016]

[Table 2]

As shown in Table 2, a black transparent substrate having a thickness of the chromium layer of about 100 ° or more and a thickness of the carbon layer of 400 ° or more was obtained. In particular, if the chrome layer is 45
When the carbon layer is 0 ° or more and the carbon layer is 500 ° or more, all are black and opaque. At this time, as the carbon thickness was increased, the color became slightly bluish, but all of them were black opaque colors.

(C) Blackening by base metal layer and carbon layer of other metal Next, instead of chromium, aluminum (Al), copper (C
u) and manganese (Mn) to a thickness of 450
カ ー ボ ン was set, and a carbon layer was formed thereon by 500 Å.
The results are as shown in Table 3, and all were black and opaque.

[0019]

[Table 3]

B, Magnetic Characteristics Next, a hard disk was manufactured using the glass substrate blackened as described above, and its magnetic characteristics were measured. For comparison of characteristics, A, B, and
A substrate C was prepared.

[0021]

[Table 4]

First, the A substrate has a chromium layer formed on a transparent glass substrate at 450 ° and a carbon layer formed thereon at 580 °.
This is a black opaque substrate formed. Next, the B substrate is a black transparent substrate in which only a carbon layer is formed at 580 ° on a transparent glass substrate. Further, the C substrate is the transparent glass substrate itself. A magnetic film was formed on each of these substrates by sputtering under the conditions shown in Table 5 to produce a hard disk.

[0023]

[Table 5]

In this table, the substrates A, B, and C are flat and have no surface textured. Then, on these substrates, the base layer by chromium 450 Å, a magnetic layer by CoCr ₁₄ Ta ₄ Alloy (atomic%) is 540Å respectively formed. Substrate heating for improving magnetic properties is performed by an IR (infrared) heater. Then, the coercive force Hc of each sample was measured while changing the heat time (heating time) in the range of 0 to 12 sec, and the graph of FIG. 1 was obtained. In addition,
Here, the heat time of 12 sec corresponds to, for example, a heat treatment in which, when an Al substrate is used, the substrate surface has a temperature of 280 ° C.

In FIG. 1, the measurement results on the substrates A, B, and C are shown in graphs GA, GB, and GC, respectively. As shown in the figure, the graph GC of the transparent glass substrate alone and the graph GB of the black transparent substrate, whereas the graph GA of the black opaque substrate has a large coercive force Hc for both, and has good magnetic characteristics. It is understood that the blackening according to the present embodiment is effectively working.

From the comparison of the graphs GA and GB, it is considered that the effect is larger when the chromium layer is also formed than when only the carbon layer is formed. The magnetization and squareness ratio were measured simultaneously with the coercive force Hc.
There was no significant difference between them for any of the substrates.

As described above, according to the present embodiment, since the metal layer and the carbon layer are formed on the transparent glass substrate and blackening is performed, the heat treatment for improving the magnetic characteristics is efficient. And good magnetic properties can be obtained in a short time.

In particular, in a magnetic recording medium, the tact time (production time per disk) is one of the important factors. In the case of using an Al substrate, the step of forming a carbon layer having a low film formation rate was rate-determining, whereas in the case of using a glass substrate, the rate of the heating step was rate-limiting. According to the present embodiment, the heating step is shortened, and the tact time is almost 3
A reduction of 0 to 40% is possible, which improves mass productivity and is advantageous in terms of cost.

The present invention is not limited to the above embodiment. For example, although the black opaque A substrate is used in the above-described embodiment, it is considered that the same or similar effect can be obtained when the density is high even if the substrate is black transparent or brown transparent. That is, if the thickness of the chromium layer in Table 2 is in the range of 100 ° and the thickness of the carbon layer is in the range of 400 ° or more, a similar effect by short-time heating can be expected.

[0030] Also, even if a metal layer other than the chrome layer is believed that similar effects from Table 3 is obtained.
Further , the present invention is particularly effective for a transparent glass substrate for a hard disk, but may be used as a base for other magnetic recording media requiring heating.

[0031]

As described above, according to the magnetic recording medium substrate according to the present invention, since the layers made of metal and carbon are formed on the transparent glass substrate, respectively, the heating is performed efficiently, and the metal layer is formed. This has the effect that excellent magnetic characteristics can be obtained and mass productivity is excellent.

[Brief description of the drawings]

FIG. 1 is a graph showing a measurement example of magnetic properties of a magnetic recording medium substrate according to the present invention and a comparative example.

FIG. 2 is an explanatory diagram illustrating a configuration of a sample in an example.

[Explanation of symbols]

10: transparent glass substrate, 12: carbon layer, 14: metal layer, GA, GB, GC: graph.

Claims (1)

(57) [Claims] In a magnetic recording medium substrate having a magnetic film on which information is recorded magnetically formed on a surface thereof, a transparent film is provided.
On glass substrate, a metal layer and 400 above 100Å thick
(4) A substrate for a magnetic recording medium, wherein a carbon layer having a thickness of not less than each is formed.